Human serum albumin (HSA) is a transporting protein that has multiple functions. The binding interaction between HSA and small molecules affects its function and efficacy of small molecules. The present study reports that kaempferol-7-O-α-L-rhamnopyranoside (KR) interacts with HSA as indicated by multiple fluorescence spectroscopy and molecular modeling. KR can quench the intrinsic fluorescence of HSA through the formation of a KR-HSA complex in a static manner. In addition, the binding site is located in subdomain IIA as confirmed by competitive experiments using site-specific warfarin and ibuprofen, and the driving forces include hydrogen bonds, van der Waals forces and electrostatic interaction derived from a thermodynamic analysis. The formation of KR-HSA is exothermic and spontaneous. Although there is no hydrophobic interaction around Tyr and Trp residues, the secondary structure of HSA changes through the formation of the KR-HSA complex. In addition, docking results visualized and further supported these results. Finally, these results can provide more information to further investigate the use of KR on the prevention of diabetic complications.
Keywords: binding interaction; flavonoid; fluorescence spectroscopy; human serum albumin; molecular modeling.